A number of different systems and structures exist for providing a drop or suspended ceiling in a room. As will be appreciated by those skilled in the art, suspended ceilings are assembled such that they are spaced a predetermined distance below the ceiling joists, in contrast to ceilings which are mounted directly on strips attached to a ceiling joist or original ceiling structure. Suspended ceilings generally comprise a plurality of individual ceiling tiles. The individual tiles may take a number of overall geometries, but are typically rectangular or square. Also, many different materials are used to fabricate ceiling tiles such as pressed fibrous materials or synthetic polymers. In particular, it is known to use synthetic resins to form precast ceiling tiles which are both lightweight, washable and durable. These precast tiles may be provided with an embossed or textured surface to add an aesthetically pleasing appearance to the tile surface which is exposed to view when installed.
The most common drop ceiling system currently in use requires a complicated track system which aligns and supports the individual tiles. It will be appreciated that for proper installation of the tiles, the grid and tiles must meet a number of geometrical requirements. That is, the faces of the tiles must generally lie in a single plane so that a uniform surface is obtained. The tiles must generally be positioned in orderly arrays of rows and columns, although in some configurations alternating rows or columns may be offset a predetermined uniform distance. In any event, the ceiling tiles are generally arranged such that a uniform pattern is created. In addition, there must be means by which the tiles can accommodate variances in the geometry of the ceiling space at corners, pillars and the like, as well as around the perimeter of the ceiling space.
In one conventional track system, after marking the height of the ceiling to be installed, a wall angle molding is attached to the walls around the inside perimeter thereof at the point where the ceiling is to be installed. The moldings are cut to length and the outside corners mitered. Main T support members must then be cut to length so that cross-T slots line up with cross-T points of the previously installed molding. The main Ts run parallel to the room center line and are perpendicular to the ceiling joists. Metal hangers are installed which support the main Ts. The main T is typically provided in sections which are connected together to form a continuous run. Cross-Ts are then installed which run perpendicular to the main Ts to form a grid that supports the individual ceiling tiles or panels. Again, the cross-Ts must be measured and cut to the proper dimensions and are then locked into the main Ts. In most instances the Ts are fabricated of metal and must be cut with tin snips or the like with any burrs and sharp edges being filed off as necessary.
One such suspended ceiling construction which describes the use of "T-bar" and "Z-bar" supporting grid structures is described in U.S. Pat. No. 4,070,840, entitled "Suspended Ceiling Construction." This prior art patent points out that grid systems of this type suffer from a number of drawbacks, including the fact that the flanges on the T bars are fully visible from below the ceiling, impairing the aesthetic qualities of the ceiling and making it necessary to employ finished metal in the T-bars so that the visible portions will be as unobtrusive as possible. Concealed grid T-bar structures are also described therein, but it is pointed out that the tiles in most such systems are not removable and must be broken to gain access to the space above as suspended ceiling.
In order to eliminate the many disadvantages associated with ceiling track systems, some effort has been made in the prior art to develop trackless ceiling systems. For example, in British patent specification 941,911 of Mar. 15, 1960, a ceiling system made up of a plurality of ceiling tiles is disclosed which does not require a true supporting grid or special substructure. More specifically, the aforementioned patent specification provides "a suspended under ceiling comprising an assembly of elements adapted to be hung up and each of which are provided with limbs or walls on all sides, characterized by the feature that the limbs or walls of the neighboring elements are interconnected together by means of connecting members, and are suspended directly from a supporting structure at individual points by means of hangers or wires." The connecting of the ceiling elements to one another may be affected for instance by means of clips, rivets, screws, adhesives or like means. For the accommodations of the connecting members the limbs or walls of the ceiling elements are provided with perforations.
In U.S. Pat. No. 3,549,114, entitled "Suspension Means For Fall Ceilings" a suspension system for ceilings composed of panels is described which is adapted to have its lower end engaged. Recesses are provided in upwardly directed flanges which are formed at the edges of the ceiling panels. The lower end of the suspension system is equipped with two differently shaped tongues, one of which is formed into a supporting hook to be engaged in a recess of the edge flanges of the tiles. The other tongue is adapted to form a safety catch which extends across the supporting hook to contact the upper edge of one of the edge flanges.
In U.S. Pat. No. 2,935,152, "Acoustical Units And Installed Assemblies Thereof" plastic forms of acoustical tiles are described which include an interlock feature between adjacent abutting tiles and an installed assembly of the tiles. It is claimed that the interlocking system aids in the precise mounting and assembly of the tiles into the desired installed positions relative to each other and functions to maintain the tiles in their assembled positions as an interlocked composite structure.
Although these purported trackless ceiling systems attempt to address the problems associated with the elimination of a supporting grid, they suffer from a number of drawbacks such as requiring difficult installation procedures, complicated or unreliable mounting structures; moreover, many prior art systems are difficult to manufacture or are otherwise unacceptable to consumers such that trackless drop ceiling systems have not gained wide spread acceptance in the marketplace.